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  Cocherell 
  — 
  Fossil 
  Parasitic 
  Hymenoptera. 
  

  

  Art. 
  XXV. 
  — 
  Some 
  Fossil 
  Parasitic 
  Hymenoptera-, 
  by 
  

  

  T. 
  D. 
  A. 
  CoCKERELL. 
  

  

  The 
  Hymenoptera 
  described 
  below 
  all 
  come 
  from 
  the 
  

   Miocene 
  shales 
  of 
  Florissant, 
  Colorado. 
  It 
  is 
  an 
  inter- 
  

   esting 
  fact 
  that 
  as 
  far 
  back 
  as 
  the 
  Miocene, 
  at 
  least, 
  the 
  

   American 
  Ichneumonoid 
  Hymenoptera 
  were 
  abnndant 
  

   and 
  varied, 
  just 
  as 
  they 
  are 
  to-day. 
  There 
  has 
  apparently 
  

   been 
  little 
  if 
  any 
  progressive 
  evolution 
  in 
  the 
  group 
  

   within 
  the 
  last 
  million 
  years, 
  although 
  there 
  has 
  been 
  a 
  

   shuffling 
  of 
  characters, 
  and 
  presumably 
  all 
  the 
  species 
  of 
  

   the 
  Florissant 
  epoch 
  have 
  become 
  extinct 
  or 
  modified 
  into 
  

   recognizably 
  different 
  insects. 
  Perhaps 
  a 
  correct 
  picture 
  

   of 
  the 
  larger 
  aspects 
  of 
  insect 
  evolution 
  is 
  this 
  : 
  "When 
  a 
  

   new 
  and 
  successful 
  mode 
  of 
  life 
  (e. 
  g. 
  the 
  parasitism 
  of 
  

   the 
  Ichneumonoids) 
  develops, 
  evolution 
  proceeds 
  rapidly 
  

   until 
  practically 
  all 
  the 
  opportunities 
  afforded 
  are 
  

   exhausted, 
  whereupon 
  the 
  group 
  enters 
  upon 
  a 
  relatively 
  

   static 
  period, 
  with 
  little 
  or 
  no 
  evolutionary 
  advance. 
  The 
  

   parasitism 
  of 
  the 
  Ichneumons 
  is 
  presumably 
  much 
  older 
  

   than 
  that 
  of 
  certain 
  other 
  groups, 
  such 
  as 
  the 
  parasitic 
  

   bees. 
  Probably 
  the 
  principal 
  developments 
  took 
  place 
  

   during 
  the 
  latter 
  part 
  of 
  the 
  Mesozoic, 
  a 
  period 
  from 
  

   which 
  we 
  have 
  very 
  few 
  insect 
  fossils. 
  

  

  Mesopimpla 
  (n. 
  gen.) 
  sequoiarum 
  n. 
  sp. 
  

  

  Length 
  12mm. 
  of 
  which 
  6 
  is 
  abdomen; 
  anterior 
  wing 
  

   8mm. 
  ; 
  width 
  of 
  head 
  slightly 
  over 
  2mm., 
  of 
  thorax 
  nearly 
  

   3; 
  hind 
  femur 
  about 
  3mm. 
  long 
  and 
  slightly 
  over 
  1mm. 
  

   wide. 
  Black, 
  including 
  the 
  femora, 
  but 
  the 
  tibiae 
  and 
  

   tarsi 
  appear 
  to 
  have 
  been 
  paler, 
  perhaps 
  ferruginous. 
  

   Antennae 
  long 
  and 
  slender, 
  the 
  joints 
  rather 
  short. 
  

   Mesothorax 
  with 
  close 
  minute 
  and 
  weak 
  punctures 
  ; 
  meta- 
  

   thorax 
  elongate, 
  with 
  at 
  least 
  two 
  parallel 
  longitudinal 
  

   carina 
  4 
  , 
  not 
  far 
  apart, 
  in 
  the 
  manner 
  of 
  Theronia 
  and 
  

   related 
  genera. 
  Hind 
  femora 
  extremely 
  stout; 
  legs 
  only 
  

   moderately 
  long. 
  Wings 
  hyaline, 
  with 
  dark 
  nervures, 
  the 
  

   essential 
  features 
  of 
  the 
  venation 
  shown 
  in 
  the 
  figures. 
  

  

  Fossil 
  Stump 
  Hill, 
  Florissant; 
  obtained 
  by 
  purchase 
  

   at 
  Florissant 
  by 
  Professor 
  "Wickham. 
  Resembles 
  Xan- 
  

   thopimpla 
  in 
  the 
  general 
  form 
  and 
  robust 
  legs, 
  and 
  also 
  

   in 
  the 
  Form 
  of 
  the 
  second 
  recurrent 
  nervure; 
  but 
  differs 
  

  

  